The invention relates to a stereoscopic camera for recording the surroundings with a right and a left image sensor, with one lens each being allocated to display the surroundings on the image sensors, with the image sensors being held by a carrier side by side and at a distance in reference to each other, and with a circuit board arranged on said carrier and provided with at least the signal and the supply lines of both image sensors.
Such stereoscopic cameras are used for various applications, in order to control the movement of a mobile device based on the optic collection and processing of the three-dimensional surroundings. In order to realize the potential functions of the device, its positioning, and also to avoid collisions when in motion it is necessary to constantly detect objects of the surroundings and their distance from the device and to supply it for real-time processing.
It is known to spatially detect the surroundings based on synchronously taking images with two imaging devices that are at a lateral distance in reference to each other when facing the object so that two images of the respective objects of the surroundings from slightly deviating directions are constantly available for processing. These stereoscopic images are subjected to special image processing in order to constantly detect the surroundings in a three-dimensional fashion.
The design of such a stereoscopic camera regularly comprises two electronic image sensors, with a lens being allocated thereto adjusted to the respective application and also the sensor. One image sensor and one lens each form one of the above-described imaging units. The image sensors are mounted on a circuit board, on which signal lines, supply lines, and if applicable at least preliminary signal processing units are arranged.
The circuit board including the described accessories is mounted on a carrier. The lens is arranged above each image sensor at a distance necessary according to the optic system of the lens. It is mounted to the carrier and the circuit board such that the image sensor is entirely encased and light only impinges the image sensors via the lenses. If necessary, the lens has a separate housing therefor.
The carrier and also its connections to the circuit board and the lens or its housing must fulfill various mechanic, thermal, chemical, and electric requirements for the different applications, where here particularly the mechanic stability is to be ensured for the use in mobile devices. For this reason, the carriers are usually made from metal.
Furthermore, the thermal expansion behavior of the carrier and the circuit board mounted fixed on the carrier influences the images taken by the camera. The different expansion coefficients of the two materials connected to each other lead to a displacement of the image sensors in reference to their objects based on the heat created by the electronic components during operation. Therefore, a loss of image quality is detected, e.g., during extended operation of a stereoscopic camera. These interferences are caused, on the one hand, by a displacement of the optic axes of the two recording units in reference to each other due to the different expansion of the carrier and the circuit board. This way, the stereoscopic images no longer overlap each other entirely so that a spatial detection of the surroundings is possible to a limited extent only or not at all. On the other hand, the interferences are caused by diffused light, which impinges an image sensor through defective connections between the carrier and the lens. The connection between the carrier and the lens is usually adhesive connections, which can tear due to the thermal expansions of the carrier and the lens.